http://arxiv.org/abs/2210.05718
The stochastic gravitational wave background (SGWB) is a rich resource of cosmological information, encoded both in its source statistics and its anisotropies induced by propagation effects. We provide a theoretical description of it, without employing the Boltzmann equation which is exclusively valid in the geometric optics limit. Our formalism is based on the so-called classical matter approximation and it is able to capture wave-optics effects, such as interference and diffraction. We show that the interaction between the gravitational waves and the cosmic structures along the line-of-sight produce an observable scalar and vector polarization. We build the two point correlation function describing the statistics of the tensor modes of the SGWB, and introduce the gravitational Stokes parameters. In the case of an unpolarized, Gaussian, statistically homogeneous and isotropic SGWB, we show that the interaction with matter does not generate a net difference between left- and right- helicity tensor modes, as expected, but it may produce Q- and U- polarization modes.
A. Garoffolo
Thu, 13 Oct 22
26/68
Comments: 30 pages plus technical appendices, 2 figures, 1 table
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